"The Joy of Federalism"

Here is Franklin Foer's recent New York Times essay, "The Joy of Federalism."  Pointing to the gay-marriage debate, to state-level stem-cell-research initiatives (a/k/a biotech boondoggles), and to some local efforts to combat "corporate abuses," Foer observes that "liberal energies once devoted to expanding the national government are being redirected toward the states."  Nor are we witnessing merely progressive opportunism, Foer insists:  "[T]he well-known liberal liking for programs at the national level has long coexisted alongside a quieter tradition of principled federalism -- skeptical of distant bureaucracies and celebratory of local policy experimentation."  After a quick re-cap of the career of New Republic founder H. Croly, Foer notes:  "For conservatives, 'states' rights' often seems just another way of asserting their libertarianism, their dislike of government in any form. Liberal federalism, on the other hand, doesn't view the state and federal governments as opposing forces."

Foer admits that "many if not most of today's liberal federalists haven't converted out of true belief[.]  Some have adopted the rhetoric of states' rights because it provides psychic relief from the alienation they feel now that a majority of the nation's voters has returned George W. Bush to office. In its most frustrated form, this alienation has manifested itself in the ubiquitous joking about emigrating to Canada. Liberal federalism provides a more rational outlet. Instead of retreating to Vancouver, liberal federalists would retreat from national politics and focus on effecting change in their own blue states -- passing health care reforms, expanding gay rights."

I wonder:  Is a principled commitment to "federalism" possible?  What should we conclude when -- to pick only one example from among many, on the right and left -- proponents of same-sex marriage celebrate the Massachusetts Supreme Court's decision and criticize the proposed Federal Marriage Amendment, on federalism grounds, on the one hand, and contend that the Constitution's equality norms require recognition of same-sex marriages, on the other?  Putting aside, for the moment, the Constitution's federalism-related and structural provisions, are there rules, standards, or guidelines that could help us, in something resembling a principled way, to identify those question that should be resolved locally, and to distinguish them from those that should be decided on a national level?  Or, does it all come down to opportunistic calculations about where we are most likely to get our way?

Rick